Some days there is no discernible noise coming from the wind turbines behind Steve and LuAnn Therrien’s house in Sheffield.

Other days, they say, the turbines create a constant roar that wakes them up in the night, makes them sick to their stomachs or their heads, drives up his blood pressure and her anxiety level, and makes their two young children restless.

“Something’s not right here,” LuAnn Therrien said.

“I’m feeling like we have to move,” Steve Therrien said, adding that they can’t afford to. “If you’re not feeling well, and you know your kids are screaming, there’s nothing you can do.”

The heated debate about wind energy in Vermont has moved to a new chapter: noise.

In Sheffield and in Lowell, some neighbors of Vermont’s two largest commercial wind projects complain the noise is driving them to distraction. The owners of the projects say they are operating the turbines within the levels allowed by the state Public Service Board, and all indications are that those levels are safe. Similar issues could arise around the new Georgia Mountain wind project, which is just starting operation.

As the Therriens and others have discovered, sound is an elusive thing that affects different people differently on different days, depending on how hard and which way the wind blows – and, some argue, even how the listener feels about wind power in the first place.

The conundrum poses a new challenge for state officials, prompting them to launch their own sound testing in Sheffield and to consider whether new sound regulations will be needed.

“These noise issues are relatively new for us,” said Geoff Commons, director of public advocacy with the state Public Service Department. “We’re trying to figure out what the problem is. We’re trying to help.”

The Therriens live off a long, dirt driveway off a long, dirt road that is dotted with a few deer camps and is a good five miles from the village of Sheffield in one direction and from Barton in the other.

Their location is about as rural as it gets, but it’s also not far as the crow flies from Interstate 91. Although they can hear the highway noise, they said the turbines are different – more persistent and not just a noise, but also a feeling.

“That never made me sick,” Steve Therrien said of the interstate.

The couple has lived there for 16 years, they said, on property that has been in his family since the 1970s. First Wind, a wind developer based in Boston, started operating the 16 turbines on the mountain less than a mile from their house in October 2011.

LuAnn Therrien started keeping a log last April of how the turbines were affecting the family. April 25, she wrote of their son and daughter, ages 3 and nearly 1, “Seager was restless. Bailey up twice.” Aug. 11, she wrote. “Kids are not sleeping well.”

In November, LuAnn Therrien wrote to President Barack Obama, telling him she feels constantly agitated.

Now in December, the Therriens say they can’t take much more. His blood pressure is up; she was given medication for depression. “It becomes worse and worse as time goes by,” Steve Therrien said.

The Therriens say they feel the effects of the noise most when the wind is blowing from the south and east. Around the other side of Granby Mountain in Sutton, Paul Brouha feels it most when the wind is coming from the north and west.

“It’s like being a block away from a beltway that has 12 lanes of traffic or next to a jet plane at 10,000 feet, but it never goes away,” said Brouha, a retired Air Force pilot who returned home to live where he grew up on land that has been in his family all his life. “It’s annoying.”

Kathy and Jim Goodrich, whose house sits down the eastern side of Lowell Mountain from the 21 turbines of the new Kingdom Community Wind Project, describe a similar experience. They fear it will be worse in the summer with the windows open.

“They’re very noisy,” Kathy Goodrich said. “I can’t live like this.”

She and her husband moved from Essex to the side of Lowell Mountain in Albany for its beauty and peace, she said, and are considering selling, if they can. “Everything we came for is gone,” she said.

Green Mountain Power Corp., which owns the Lowell wind project that started operating last month, has received noise complaints from 28 households, spokeswoman Dorothy Schnure said.

Despite the complaints, operators of both the Lowell and Sheffield projects say the turbines are running within the noise limits allowed. The state Public Service Board requires them not to exceed 45 decibels outside an existing residence and 30 decibels inside, according to the board’s requirements. Both projects are required to conduct quarterly sound monitoring at four locations each.

The Lowell project got off to a bit of a rough start the weekend of Nov. 4, when area residents said the noise was especially loud.

Don and Shirley Nelson, who live on the Albany side of the mountain and have been fighting the project for years, said the noise sounded like a jet engine directly overhead. They collected 30 names on a petition in complaint that weekend. They didn’t call Green Mountain Power, because they said they didn’t think they’d have any standing with a company they’ve been fighting for so long in court and before state regulators.

“People complained, but not to us until Monday night,” Schnure said. “I wish people would complain to us when something happens so we could, No. 1, experience it, and No. 2, take care of it.”

Green Mountain Power acknowledged there was a unique problem that weekend with ice buildup on the turbine blades as temperatures hovered around freezing in dense fog, Schnure said. Neighbors who say the turbines are still bothersome concur it hasn’t been as bad as it was that weekend.

On top of the mountain, there are things operators of the turbines can do to mitigate noise, by changing the pitch of the blades, said Doug Manning, lead technician and planner for Vestas, which operates the turbines for the utility. Schnure said experience, and the results of sound testing, will tell Green Mountain Power when to put the turbines in noise-reduction mode.

The Goodriches say they have started calling Green Mountain Power representative Lucy Leriche with their complaints, and she has been responsive, but they wonder whether the complaints will solve their problem.

Schnure said she’s not surprised by the noise complaints, because opponents of the project said they were going to complain about the noise when they lost the fight over environmental and aesthetic issues.

“There are tens of thousands of turbines installed around the world. There are not a lot of people saying, ‘They are making me sick,’” Schnure. “There are some. Whether it’s turbines or stress or some other factor, I don’t know.”

A Massachusetts study released this year found “limited evidence” of a link between exposure to wind turbines and annoyance, and no evidence linking wind turbines with high blood pressure, hearing loss or headaches.

Dr. Harry Chen, Vermont’s health commissioner, said he has found no evidence that turbine noise is harmful to a person’s health. He said he went to Sheffield a couple months ago on a windy day to hear the turbines for himself.

“You really could barely tell,” he said of the sound. “I didn’t see anything that alarmed me at all.”

But Chen said he also believes more studies need to be done as changes in wind-turbine technology change the level of noise. He said he is watching a study by Health Canada due to be completed in 2014 and hopes it will offer insight into whether Vermont should adjust its noise-level standards.

Critics already have poked holes in the Canadian study, saying it will not provide definitive answers despite a $1.8 million price tag.

Meanwhile, a U.S.-British study of turbines in Maine this year found that those living near turbines had poorer-quality sleep than those who lived farther away.

Schnure, the Green Mountain Power representative, pointed to studies that indicate those who are opposed to wind projects are more likely to find the sound offensive than those who support them.

There is evidence in the Kingdom that is proving to have validity. In Lowell, where residents overwhelmingly supported the project, complaints have been almost nonexistent, said Selectboard Chairman Richard Pion. He lives on Irish Hill Road, within 4,000 feet of the turbines, and said he can’t hear them in his house.

In Albany, which took its challenge of the project to the state Supreme Court, residents are unhappy with the noise, said Selectboard Chairman Carl Chaffee. “I think we got railroaded,” he said.

While both towns will receive some money from Green Mountain Power for the project, Lowell, as the host, stands to receive more.

Les Bloomburg, a noise expert in Montpelier who’s been working with neighbors of the Sheffield and Lowell projects, said research indicates those who feel there is a benefit from a noise will tolerate the sound better. He also said those who have had positive interactions with those making the noise will react better.

“If you create a whole lot of animosity in a community, it’s going to come back to haunt you,” he said. “If you’re open and cooperative, then you buy goodwill.”

In Sheffield, he said, First Wind has declined to share the raw data that goes into its reports, a move he suggested was not buying much goodwill.

Tests show compliance

Sheffield, a project that began operating in October 2011, has produced a year’s worth of sound-monitoring reports from four monitoring stations. The reports all cite no problems with the sound limits.

“Everything we’ve done shows the project well within the established guidelines,” said John Lamontagne, spokesman for First Wind, owner of the Sheffield project.

The Lowell project has just started collecting its first set of sound data. At Lowell, Green Mountain Power spokeswoman Schnure said, the two-week sound-monitoring process requires operators to shut down the turbines for 20 minutes every three hours. Results from Lowell will not be available until the data are collected and analyzed by a third party, Schnure said.

Gabrielle Stebbins, executive director of Renewable Energy Vermont, said Sheffield’s sound reports show that the background noise in some cases, including I-91, is greater than the turbine noise. Many everyday noises inside people’s homes reach the maximum allowable for the turbines, she said.

Bloomburg, the noise expert, saw the reports differently. Although they conclude the sound from the turbines does not exceed the limits, he takes issue with the testing. He said having one of the monitoring stations close to I-91 was a mistake, because it didn’t allow the test to isolate the turbine sound. Instead, it allowed the testers to conclude they couldn’t discern the noise. He said the monitoring should be done closer to the turbines.

State officials have heard the complaints, not just about the noise but about the sound monitoring. After former Public Service Commissioner Liz Miller (now Gov. Shumlin’s chief of staff) visited the Sheffield project this fall, she directed her department to have more sound testing done.

Miller’s successor as commissioner, Chris Recchia, said depending on the results of the testing, the department could seek changes in the noise standards.

“We need to look at the data,” he said. “I’m trying to keep an open mind about it.”

He said the state is taking into account questions raised by the turbine opponents about whether the tests should measure for infrasound, or low-frequency sound. The Public Service Board specified that the project developers did not have to test for that.

Recchia’s boss, Gov. Shumlin, has been clear. He supports wind energy as a way of reducing Vermont’s dependence on coal-fired, nuclear and other traditional sources of energy. Shumlin has set a goal that 90 percent of the state’s energy come from renewable sources by 2050.

LuAnn Therrien said the state-hired sound tester arrived last week, but she worried whether he’d get an accurate reading. Despite Friday’s high winds, she said, the turbines were uncharacteristically quiet. She wondered if that was on purpose.

Lamontange, the First Wind spokesman, said the company would not alter the operation of the turbines to make them sound quieter for the test. “Of course, we don’t make any adjustments when testing is going on,” he said.

Critics are working on their own testing. Annette Smith, executive director of Vermonters for a Clean Environment, said her group raised $2,000 to buy sound-monitoring equipment and has somebody learning to use it.

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